Project Summary We aim to develop and assess the feasibility, acceptability, and preliminary efficacy on adherence of a community-informed tenofovir/emticitrabine (TDF/FTC) pre-exposure prophylaxis (PrEP) engagement intervention among street-based female sex workers (FSWs) in Baltimore, Maryland. PrEP is a potentially empowering method of HIV protection that is safe and effective, however, there is little research to inform PrEP targeting and use among FSWs. The CDC Clinical Guidelines indicate PrEP for women engaged in sex work. Through a community participatory process, we propose developing a small group, mHealth-enhanced peer- navigator intervention, STAR-PrEP (Sex workers Take Action and Responsibility), aimed raise PrEP awareness among FSWs and to to enhance PrEP uptake and adherence. The study is informed by psychological empowerment and fundamental cause theories. The study aims to: 1). employ community engaged research activities (e.g., community forums, focus groups, component testing, in-depth interviews) to identify FSW-specific barriers to PrEP engagement and to develop a small group and mHealth enhanced SW- PrEP intervention to promote PrEP uptake and adherence among street-based HIV-negative FSWs (N=40) in Baltimore Maryland; 2) assess the STAR-PrEP?s acceptability (e.g., refusal rates, intervention engagement) and feasibility (e.g., recruitment, retention) among intervention participants (n=40), and preliminary efficacy on PrEP uptake and adherence in intervention versus comparison participants (n=40) among street-based FSWs in Baltimore, Maryland at 6-month follow-up; 2a) to explore the role of empowerment (e.g. perceived stigma, social support) and structural vulnerability (e.g., access to care) factors as correlates or possible mediators of the intervention effect on study outcomes in intervention (n=40) versus comparison participants (n=40) at 6-month follow-up; and 3) to explore predictors (i.e., homelessness, depression, drug use) of STAR- PrEP participants on monthly drug adherence among street-based FSWs (N=40) in Baltimore, Maryland at the 6-month follow up. Drug adherence will be detected by 6-monthly plasma and peripheral blood mononuclear cells tests. The proposal is directly responsive to RFA-MH-17-361 and addresses 3 NIH HIV/AIDS Research Priorities: 1) reducing ?incidence in HIV/AIDS? among a high risk yet understudied population; 2) reducing health disparities among socially and economically marginalized group of women who are largely African American; and 3) training peer navigators to increase a ?workforce to conduct high priority HIV/AIDS research. The proposed intervention is one of the first to focus on this high-risk yet understudied population in the U.S., and is strengthened by its partnership with longstanding community healthcare providers to prescribe PrEP. Data will inform the design, recruitment, and effect size of a future R01 focused on a larger trial targeting street-based FSWs and PrEP providers.